Positionable vehicle



Jan. 28, 1969 i 2 R. c; cousms ET AL 2 3,424,272

POSITIONABLE VEHICLE Filed Dec. 27, 1966 Sheet of 5 RICHARD C. COUSINS EUGENE A. COOLEY WAYNE C. WORSTELL JAMES L. EATON INVENTORS BY BUCKHORN, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEYS Jan. 28, 1969 I c, cous s ET AL 3,424,272

POSITIONABLE VEHICLE Filed Dec. 27; 1966 RICHARD C. COUSlNS EUGENE A. COOLEY WAYNE C. WORSTELL JAMES L. EATON INVENTORS BUC/(HORN, BLORE, KLAROU/ST 8 SPAR/(MAN ATTORNEKS United States Patent 3,424,272 POSITIONABLE VEHICLE Richard C. Cousins, Eugene A. Cooley, Wayne C. Worstell, and James L. Eaton, Portland, Oreg., assignors to Albina Engine and Machine Works, Inc., Portland, Oreg., a corporation of Oregon Filed Dec. 27, 1966, Ser. No. 611,203 U.S. Cl. 18216 Claims Int. Cl. E04g 1/24, 1/18 ABSTRACT OF THE DISCLOSURE A hydraulically driven and steered wheeled vehicle which can be driven from place to place and then tied down for performance of certain operations. When the vehicle is tied down, the supply of hydraulic fluid is terminated to the hydraulic steering means and the hydraulic drive means.

This invention relates to a positionable vehicle useful for safely supporting a platform or scaffolding at the side of a building and particularly to such a vehicle exhibiting a high degree of mobility and maneuverability.

Scaffolding is frequently employed at the side of a building for performing such functions as window washing, painting and making repairs. One type of scaffolding comprises a platform suspended from the building roof upon cables or ropes, the latter being used for raising or lowering the platform along the building wall. With this scaffolding a vertical strip area of the building wall may be reached which area is substantially as wide as the length of the suspended platform. If other areas are to be reached, the platform must be movable horizontally as well as vertically.

An apparatus for providing horizontal movement of a suspended platform while also securely supporting the same is set forth and claimed in Cousins et al. patent, No. 3,245,355. In this patent, the apparatus comprises a pair of vertically spaced parallel tracks or rails secured to a building. These tracks or rails engage sets of wheels in turn supporting a crane from which the platform or scaffolding is suspended. Since the tracks are attached to the building and the crane wheels are tightly secured for travel only upon the tracks, safety of platform support is attained while considerable mobility of scaffolding movement is also achieved.

However, the use of the movable scaffolding as described above is, of course, restricted to buildings including rail installations. In many buildings it is not possible or practical to install rails along a roof edge or elsewhere on the building.

It is therefore an object of the present invention to provide an improved positionable vehicle which may be used to support a scaffolding or the like, such vehicle combining safety of operation with enhanced mobility.

It is another object of the present invention to provide an improved scaffolding supporting vehicle which may be easily maneuvered along the roof edge of almost any building and which safely supports a platform relative to such edge.

It is another object of the present invention to provide an improved positionable and portable vehicle Which may be used in supporting a scaffolding, platform, or the like,

3,424,272 Patented Jan. 28, 1969 and which does not require a permanent support installation.

It is a further object of the present invention to provide an improved positionable vehicle having the advantages of maximum maneuverability and safety of operation, such vehicle also being of inexpensive construction.

It is a further object of the present invention to provide an improved positionable vehicle which may be conveniently driven and positioned by one operator.

It is a further object of the present invention to provide an improved hydraulically steered and driven positionable vehicle of simplified and inexpensive construction.

Briefly, an embodiment of the present invention includes an hydraulically driven and steered vehicle for supporting a vertically movable platform at one side thereof. The vehicle is provided with a counter-balanced frame mounted upon sets of front and rear wheels, these sets of Wheels being hydraulically steered independently from each other. Separate hydraulic drive means are also mounted directly upon one or more sets of wheels. An operating station on the vehicle includes steering control means for the rear set of wheels and oppositely located steering control means for the front set of wheels, with forward and reverse direction drive control means located therebetween. This operating station is preferably located at the same side of the vehicle as the vertically movable platform. An operator at this station can maneuver the vehicle and the platform it supports into any position along a building roof edge or parapet from almost any other position.

Means are provided for securely anchoring or tying down the vehicle at a desired location at a building roof edge or other working surface. The tie down means includes means for disabling the hydraulic steering and hydraulic drive apparatus when the vehicle is thus secured so that dangerous movement of the vehicle while the platform is in use is avoided. In addition, the tie down means disables the supply of power to the platform except when the vehicle is properly secured. Thus, not only is a high degree of mobility and maneuverability attained for moving the scaffolding platform at the proper time, but also a desired factor of safety is attained.

The subject matter which we regard as our invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, both as to organization and method of operation, together with further advantages and objects thereof, may best be understood'by reference to the following description taken in connection with the accompanying drawings wherein like reference characters refer to like elements and in which:

FIG. 1 is a perspective view of a positionable vehicle according to the present invention;

FIG. 2 is a detailed drawing partially broken away, illustrating hydraulic steering means for the positionable vehicle;

FIG, 3 is a detailed drawing partially in cross section of hydraulic drive means;

FIG. 4 is a partial view of tie down means provided for the positionable vehicle;

FIG. 5 is a schematic hydraulic and electrical diagram for hydraulic and electrical connections employed within the vehicle; and

FIG. 6 is a partial side view illustrating an alternative control arrangement.

Referring to the drawings, a positionable vehicle according to the present invention comprises a frame including a deck 10, and support means including vertical forward legs 12 and 14 and vertical rear legs 16 and 18. The forward legs 12 and 14 are separated by means of horizontal cross brace 20 while rear legs 16 and 18 are similarly separated by means of horizontal cross brace 22. Deck carries a first davit or boom 24 secured to deck 10 at one side thereof and extending laterally across the vehicle and outwardly from the opposite side of the vehicle. A second davit or boom 26 at the opposite end of the vehicle is also secured at one side of deck 10 and also extends across the vehicle and outwardly from the opposite side of the vehicle. Boom 24 is vertically supported at the remote side of deck 10 upon upright member 28 while boom 26 is similarly supported upon upright member 30.

The booms 24 and 26 include horizontally extending portions 32 and 34 having the cross sections of l-beams. These horizontally extending portions 32 and 34 support trolleys 36 and 38, which travel along the lower flanges of the I-beam cross sections. Trolleys 36 and 38 in turn suspend a vertically movable platform 40 from vertical cables 42 and 44, joining the platform to the respective trolleys. Each cable, for example cable 44, extends to a hoisting mechanism 46 mounted on platform 40, the latter including a controllable winch for raising and lowering platform 40 with respect to boom extensions 32 and 34. Mechanism 46, and a similar mechanism at the opposite end of the platform, are suitably electrically operated and receive power from a reel 48 for paying out electrical cable 50 over pulleys 52 and 54 mounted on boom 26. As the platform 40 is raised and lowered, reel 48 supplies a just sutficient length of power cable for reaching the platform. Reel 48 is operated by motor 56 which may be electrically powered or spring powered.

The platform 40 may be lowered over the edge of a building or the like from the top edge of the building to any desired position along the side of the building. It is understood that the vehicle frame including deck 10 is desirably weighted to counter-balance platform 40. Rollers 58 protect the platform 40 from the building, and a railing 60 suitably encloses the platform horizontally for the safety of personnel carried thereon, and may include wire screening between railing members. Shelf member 220, and a similar shelf member at the opposite end of the deck, may be slid out from under the deck to support the platform in an upraised position thereof.

The rear support means for the vehicle further includes a pair of fork-shaped yokes 62 and 64 respectively mounted at the ends of legs 16 and 18, and which are vertically rotatable about the vehicle axes of the respective legs, for example upon caster bearings 65. The yokes also include respective sprockets, 66 and 68, secured to each yoke for turning the yokes on their caster bearings. A chain drive engages the sprockets and includes a single chain 70 for simultaneously engaging both sprockets 66 and 68. The ends of this single chain are joined to actuating rods 72 and 74 extending from either end of double acting hydraulic cylinder 76, the latter being supported upon cross brace 22. Since each actuating rod of hydraulic cylinder 76 is joined to one end of chain 70, each such actuating rod acts to turn both yokes 62 and 64 simultaneously by pulling action of the chain. This pulling action is preferred to an arrangement wherein each actuating rod must operate each yoke by both pulling and pushing action, since the actuating rods in the present system may be smaller and the steering mechanism less expensive.

Chain 70 includes a turnbuckle 78, conveniently included in the chain on the opposite side thereof from cylinder 76 and used for adjusting the chain to providerelative to yoke 64 such that these yokes are maintained in a desired parallel attitude. Such means includes a connecting nut 80 threaded to receive a threaded end 82 of rod '72, and a lug portion 84 bored to receive a pin of chain 70. A jam nut 86 holds connecting nut 80 in any position of adjustment relative to the threaded end of rod 72. By suitably adjusting the connecting nuts, correct parallel alignment of the yokes can be obtained. Of course the chain will be placed on the sprockets 66 and 68 with the yokes substantially aligned, and the connecting nuts 80 and 86 will then be adjusted to attain substantially exact alignment.

Yokes 62 and 64 carry rear wheels 88 and 90, respectively, which are journaled in ball bearings, e.g., bearings 92, carried by the yoke (see FIG. 3). Wheels 88 and 90 are also provided with rubber tires 94 and 96 resting upon the working surface over which the vehicle travels, for example the roof of a building or the like.

Wheel shaft 98, keyed to the hub 100 of wheel 88, is tubular and receives therewithin the drive shaft 102 of hydraulic drive motor 104. Hydraulic drive motor 104 is secured to the yoke by means of bolts 106 such that drive shaft 102 is coaxial with wheel shaft 98. This drive shaft passes through an opening in end plate 108 and is keyed to wheel shaft 98. Since the hydraulic drive motor 104 is mounted directly on the yoke with its output shaft coaxially joined to the hub of the wheel, no intermediate gearing or other mechanism is required between the drive motor and the wheel. Flexible hydraulic lines 110 connect the drive motor 104 to the vehicles hydraulic system and these flexible lines allow the wheels to be steered without binding or adversely affecting the vehicles drive operation.

Rear wheel 90 is driven by a hydraulic motor 112 mounted directly on yoke 64 and having its output shaft coaxially joined to the hub of wheel 90. The details of this construction are substantially the same as described in connection with wheel 88, and therefore this description will not be repeated.

The vehicle also includes a pair of front wheels 114 and 116 carried by yokes 118 and 120 the latter being respectively journaled for vertical rotation at the lower ends of legs 12 and 14. Wheels 114 and 116 are similarly provided with rubber tires 126 and 128 for riding upon the Working surface. A double acting hydraulic cylinder 122 drives a single chain 124 simultaneously engaging sprockets joined to yokes 118 and 120 for turning the same. The other details of construction of the front wheels and the steering mechanism are substantially identical to those already discussed to connection with the rear wheels, except that no drive motors are mounted on yokes 118 and 120 for driving the front wheels in this embodiment. Suflicient drive and maneuverability for most purposes is achieved with drive to the rear wheels only.

Hydraulic drive motors 104 and 112 as well as double acting hydraulic cylinders 76 and 122 are coupled by means of hydraulic circuitry, hereinafter described, to a control station on deck 10, generally indicated at 130. At the ends of this control station are located facing steering wheels 132 and 134, mounted to operate spool valves 136 and 138 for respectively positioning the hydraulic cylinders 76 and 122. The steering wheels 132 and 134 are preferably located at the side of deck 10 next to boom extending portions 32 and 34 and from which platform 40 is suspended. The turning axis of each of these steering wheels is substantially parallel with the side of deck 10.

A four-way control valve 140 provided with a control handle 142 is located at control station between the steering wheels. This four-way control valve has both forward and reverse control positions for causing rotation of hydraulic drive motors 104 and 112 in forward and reverse drive directions. Thus, the positionable vehicle is controllable by an operator at station 130 for movement with independent control of direction of movement of the front and rear wheels.

With independent control of the steering for both the I front and rear sets of wheels, it is possible to maneuver the vehicle along a roof edge or parapet of a building while the platform 40 is suspended from the booms. The vehicle with platform may be moved completely up against a corner of a building parapet with both front and back pairs of wheels disposed for travel parallel to the edge of the roof. Then the front pair of wheels may be turned at substantially right angles while the rear wheels are maintained in position so the vehicle may be driven around the corner. Meanwhile the vehicle is maintained in close proximity to the roof edge. A similar maneuver may be executed at nearly any wall juncture.

Also, the vehicle may be driven sideways up to the roof edge when desired. For example, if the vehicle is preliminarily driven to a position obliquely oriented relative to the roof edge, it is possible to move only the end of the vehicle, furthest away from the roof edge, directly towards the edge without disturbing the position of the other end of the vehicle and without substantially disturbing the position of the vehicle in a longitudinal direction.

It is apparent that a high degree of flexibility is attained for achieving nearly any desired position or series of positions of the vehicle and the platform which it carries. Moreover, vehicle control is at the direction of a single operator who may substantially simultaneously steer the front and rear wheels of the vehicle by means of the facing steering wheels 132 and 134 at the operators station, while also controlling the forward and backward movement of the vehicle with valve 140. The centralization of these controls and the positioning thereof at the platform side of the vehicle provides for optimum supervision.

A desirable control station alternative is illustrated in FIG. 6. In FIG. 6, similar elements are designated by primed reference numerals. Thus, spaced steering wheels, numbered 132' and 134, control spool valves, numbered 136 and 138 respectively. It is again understood that these steering wheels are located in facing relation preferably at the side of the vehicle closest to platform 40. In the FIG. 6 modification, control valve 140' is no longer provided with a control handle, but it is rather provided with a foot treadle or rocking plate 144 secured for rotation at pivot 146. The rocking plate 144 also pivotally engages the end of the valves control rod 148 whereby movement of the rocking plate in the direction shown by the arrow around pivot 146 withdraws and inserts the control rod with respect to valve 140. An operator at the control station illustrated in FIG. 6 may thus control one of the steering wheels with each hand and the rocking plate 144 with one foot, while also observing the position of platform 40 relative to the building. In an instance where it is desired that both front and rear wheels be powered, both front and rear drive wheels may be controlled with the same foot or hand valve, or separate foot or hand valves may be supplied, for example with one valve for the front wheels and one valve for the rear wheels.

Once the positionable vehicle is appropriately located, it is desired that the vehicle be secured to the working surface, i.e., the roof on which the vehicle is driven, for reasons of safety of platform support. It is desired the vehicle be secured before the platform 40 is altered in its vertical position relative to boom extending portions 32 and 34. For this purpose, there is provided a tie down means for securing the vehicle to the working surface, such means including switching means for providing power to the platform 40 only when the vehicle is thus secured. Furthermore, the tie down means is also provided with switching means for preventing any movement of the vehicle relative to the working surface when the vehicle is thus secured.

The tie down means includes a flexible anchoring means in the form of a chain 150 for attachment to the working surface at the chains lower extremity. The tie down means is effective to place this chain 150 under tension for thereby securing the vehicle and the platform. The tension is also effective to operate the switching means for disabling vehicle movement while also appropriately providing power to the vertically movable platform.

Referring particularly to FIG. 4, the tie down means includes a base plate 152 secured to deck 10 by means of bolts 154 at the side of the deck opposite platform 40. The central member of the tie down means comprises a threaded nonrotatable rod 156 passing through openings provided in plate 152 and deck 10, rod 156 being secured at its lower extremity to chain 150. Rod 156 is keyed so that it may not rotate, but it nonetheless may move in a vertical direction, whereby it may be used to take up the slack in chain 150. A rotatable control wheel 158 is mounted coaxially upon rod 156 and includes a central internal thread for engaging threaded rod 156.

Control wheel 158 also rests upon circular element 160 which in turn is supported upon compressed spring 162 located between element 160 and base plate 152. When control wheel 158 is rotated in a right hand direction, the internal threads thereof, mating with threaded rod 156, cause the rod 156 to raise the chain 150 in an upward direction. As the slack in the chain is taken up and the chain becomes taut, further rotation of control wheel 158 is possible only as the same moves downwardly against the biasing compression of spring 162. As control wheel 158 is further rotated, element 160 is also forced downwardly.

Just under element 160, a first microswitch 164 is located which is secured upon support 168 in turn mounted on base plate 152. A second microswitch 170 is located on support 172 with the latter also being mounted on base plate 152. One of these microswitches is employed to disable movement of the vehicle when the tie down means is secured, while the other microswitch is employed for energizing the platform when the tie down means is in secured position. While separate microswitches are employed for these purposes, it is apparent that a single switch or switching means could be employed if so desired. As the control wheel 158 is tightened, element 160 will be forced against microswitches 164 and 170 whereby both such switches are operated. Thus, not only is the vehicle completely secured to the working surface by means of the tie down means, for preventing tipping or movement of the vehicle by the weight or movement of platform 40, but also the vehicles power is appropriately controlled in a manner consistent with its secured or nonsecured position as the selected case may be.

Hydraulic and electrical circuitry employed with the positionable vehicle according to the present invention is illustrated in the schematic diagram of FIG. 5. Referring to FIG. 5, hydraulic supply 174 includes a pump 176 connected to a strainer 180 and driven by electric motor 178. The pump 176 provides hydraulic fluid at outlet connection 182, the latter also being connected to reservoir 184 by way of relief valve 186. The power for electric motor 178 is derived from power line 188, the latter ultimately taking the form of a trailing supply cord for the vehicle. Power line 188 is connected to electric motor 178 through contactor 190 having contacts which are closed by means of operating coil 192. The operating coil 192 is also connected to the supply line through microswitch 170 operated by the tie down means (see FIG. 4). Microswitch 170 is provided with normally closed contacts and therefore operating coil 192 will close the contactor to supply power to electric motor 178 only when the tie down does not secure the vehicle to a working surface. When the tie down secures the vehicle to a working surface, microswitch 170 is opened and the electric motor 178 no longer drives pump 176. The vehicles hydraulic system is thereby disabled.

Output connection 182, having pressure gauge 194 connected thereto through valve 196, supplies hydraulic fluid to four-way valve 140 operated by its control handle indicated at 142. In the center or neutral position of the valve 140, the hydraulic fluid is delivered directly to flow equalizer 198 and from there to spool valves 136 and 138 connected for steering the vehicle. In the neutral position or center position indicated for valves 136 and 138, hydraulic fluid is returned Via line 200 to reservoir 184 by way of filter 202. However, if valve 136 is turned by means of steering wheel 132, hydraulic fluid will be delivered to double acting cylinder 76 through lines 110, causing rods 72 and 74 to move either towards the left or towards the right according to the direction the steering wheel is turned. As previously described, movement of double acting hydraulic cylinder 76 causes the rear wheels of the vehicle to change their direction for steering of these wheels. When the rear wheels have turned to the steering direction desired, valve 136 will return to its center position. A hydraulic steering system of this type is described in Charlson Patent 2,984,215. 7

Similarly, spool valve 138 under the control of the steering wheel indicated at 134 is connected to double acting cylinder 122 by way of hydraulic lines 204. AS hereinbefore indicated in the previous description of the vehicle cylinder 122 is employed for steering the front wheels of the vehicle. When spool valve 138 is in neutral position, hydraulic fluid is returned to the supply via line 200. This hydraulic steering system is substantially the same as the one described for the rear wheels.

Four-way valve 140 is employed to direct hydraulic fluid in either a forward or reverse direction through drive motors 104 and 112 mounted on the vehicles rear wheels. For forward operation, hydraulic fluid leaves valve 140 by way of line 206 and divides in flow equalizer 208 for application to the two motors. Hydraulic fluid returns by way of flow equalizer 210 and line 212, through valve 140 to flow equalizer 198 from which fluid is directed to the steering system. Lines 206 and 212 are cross connected with relief valves 214. With the valve 140 in its reverse position, hydraulic fluid enters line 212 and divides at equalizer 210 for application to motors 104 and 112 causing them to drive the vehicle in the reverse direction. In this case, hydraulic fluid returns via equalizer 208 and line 206, through valve 140 to equalizer 198. In this system, the hydraulic return from the drive system is connected to the steering system in order to reduce the number and length of hydraulic lines required for the wheel drive and steering mechanisms.

The platform derives its power through cable 50 by way of contactor 216 employed for connecting the cable to power line 188. Contactor 216 is operated by means of operating coil 218 connected to power line 188 through microswitch 164 (see FIG. 4). When the tie down secures the vehicle to a working surface, microswitch 164 is closed, thereby energizing operating coil 218 for closing the contactor 216. Therefore, power is supplied to the vertically movable platform only at such times as the tie down secures the vehicle. Electrical and hydraulic equipment for the vehicle is generally indicated at location 220 in FIGURE 1.

While we have shown and described a preferred embodiment of our invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from our invention in its broader aspects. We therefore intend the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

We claim:

1. A positionable vehicle comprising:

a frame,

front support means carrying a pair of front wheels upon which said vehicle is movable,

a rear support means carrying a pair of rear wheels upon which said vehicle is also movable,

hydraulic steering means for independently controlling the direction of orientation of said pair of front wheels and of said pair of rear wheels,

hydraulic drive means for rotating at least a selected pair of wheels for moving said vehicle,

a common hydraulic supply for said hydraulic steering means and said hydraulic drive means, and

tie down means for securing said frame in a fixed position relative to a working surface upon which said vehicle is movable and including means operated by said tie down means to terminate the supply of hydraulic fluid to said hydraulic steering means and said hydraulic drive means when said frame is thus secured to said working surface,

2. The vehicle according to claim 1 including electric power means for operating said hydraulic supply and electrical switch means interconnected with said electric power means and operated by said tie down means to interrupt the source of power to said hydraulic supply when said tie down means secures said frame in a fixed position relative to a working surface.

3. The vehicle according to claim 1 wherein said tie down means includes a flexible anchoring means for attachment to said working surface at one end thereof, a threaded nonrotatable rod member mounted for vertical movement on said frame and having said flexible anchoring means secured to its lower end,

a rotatable control wheel coaxial with said rod member and threaded at its center to engage said rod member,

spring biasing means for urging said rotatable control wheel upwardly with respect to said frame, and

means vertically movable with said rotatable control wheel located above said means for disabling said hydraulic supply for engaging said means for disabling said hydraulic supply as said rotatable control wheel is rotated raising said rod member against the bias of said spring biasing means, said rotatable control wheel lowering upon said disabling means as said flexible anchoring means restrains further upward movement of said rod member.

4. The vehicle according to claim 1 wherein said tie down means includes a flexible anchoring member for attachment to said working surface, and means for securing said flexible anchoring member to said frame,

said last mentioned means including means for ten-' sioning said flexible anchoring member including an element which is constrained to move as said flexible anchoring member is placed under tension, and

switching means operated by said element comprising the said means for disabling said hydraulic supply, said switching means being engaged by movement of such element.

5. The vehicle according to claim 1 further including a platform carried by said frame and movable in a vertical direction, and motive means for adjustably elevating and lowering said plat-form.

6. The vehicle according to claim 5 including a pair of shelf members normally received within said frame and partially slidable horizontally from said frame for supporting said platform in one vertical position thereof.

7. The vehicle according to claim 5 including power supply means for said motive means, and wherein said tie down means further includes means for disabling said power supply means except when said frame is secured by said tie down means to said working surface.

8. The vehicle according to claim 7 further including a pair of booms extending laterally from said frame and a vertical suspension system depending from said booms for supporting said platform under said booms.

9. The vehicle according to claim 1 wherein said hydraulic steering means for independently controlling the direction of orientation of said pair of front wheels and of said pair of rear wheels includes a first steering wheel mounted on said frame with a hydraulic steering connection means between said first steering wheel and said pair of front wheels for steering the same, and a second steering wheel mounted on said platform in facing relation to said first steering wheel, and a hydrauulic steering connection means between said second steering wheel and said pair of rear wheels for steering the same.

10. The vehicle according to claim 9 further including a control member for operating said hydraulic drive means wherein said control member is located between said steering wheels whereby one individual can conveniently control both steering wheels and said control member.

11. The vehicle according to claim 10 wherein said control member includes a hydraulic valve connected to operate said hydraulic drive means selectively in forward and reverse directions, and wherein said control member includes a foot pedal operatively connected to said hydraulic valve, said foot pedal being mounted between said facing steering Wheels on said frame for convenient foot operation by an individual operating both said steering wheels.

12. The vehicle according to claim 1 wherein one of said support means carrying a pair of wheels comprises first and second fork-shaped yokes mounted on the underside of said frame of said vehicle, said yokes being mounted for rotation about vertical axes with each yoke carrying one of said pair of wheels, and

wherein said hydraulic drive means comprises a pair of hydraulic motors, one mounted on each said yoke and having its output shaft coaxially poined to the hub of the wheel carried by said yoke.

13. The vehicle according to claim 1 wherein said front support means carrying a pair of front wheels comprises first and second yokes mounted for rotation about vertical axes at the front of the vehicle, each yoke carrying a wheel for supporting said vehicle, and wherein said rear support means carrying a pair of rear wheels comprises first and second yokes mounted for rotation about vertical axes at the rear of the vehicle, each yoke carrying a wheel for supporting said vehicle, and

wherein said hydraulic steering means comprises a first single driving chain for simultaneously engaging the first and second yokes of said front support means for simultaneously rotating the same about their vertical axes and a double acting hydraulic cylinder connected to the ends of said chain for moving said chain to turn said yokes, and

wherein said hydraulic steering means also comprises a second single driving chain for simultaneously engaging the first and second yokes of said rear support means for simultaneously rotating the same about their vertical axes and a double acting hydraulic cylinder connected to the ends of said chain for moving said chain to turn said yokes.

14. The vehicle according to claim 13 including adjustable means between said double acting hydraulic cylinder and said chain for adjusting the relative orientation between a pair of yokes to adjust the parallel tracking of the wheels carried by said pair of yokes.

15. A positionable vehicle comprising:

a frame,

front support means carrying a pair of front wheels upon which said vehicle is movable, rear support means carrying a pair of rear wheels upon which said vehicle is also movable,

steering means for independently controlling the direction of orientation of the front and rear wheels of said vehicle,

drive means for driving at least selected wheels of said vehicle, and

tie down means for securing the frame in a fixed position relative to a working surface said tie down means including a flexible anchoring member for attachment at one end thereof to said working surface, and tensioning means on said vehicle connected to the opposite end of said flexible anchoring member for placing said anchoring member under tension to secure said frame to said working surface, said tie down means being further provided with switching means for disabling the operation of said vehicle only when said tensioning means is under tension for securing said vehicle, said tensioning means including an operating member for operating said switching means only when said tensioning means is under tension.

16. A positionable vehicle comprising:

a frame,

front support means including a pair of fork-shaped yokes mounted on the underside of said frame of said vehicle for rotation about vertical axes and carrying front wheels for supporting said vehicle,

rear support means including a pair of fork-shaped yokes mounted on the underside of said frame of said vehicle for rotation about vertical axes and carrying rear wheels for supporting said vehicle,

hydraulic drive means for said rear wheels comprising hydraulic motors mounted on the yokes carrying said rear wheels, each of said motors having its output shaft coaxially joined to the hub of one of said rear wheels,

hydraulic steering means for independently controlling the direction of orientation of said pair of front wheels and the direction of orientation of said pair of rear Wheels, said hydraulic steering means including sprockets joined to each of said yokes for moving said yokes about their vertical axes, a first chain drive for the yokes of said front support means including a double acting hydraulic cylinder and a chain simultaneously engaging the sprockets of the yokes carrying said front wheels, the ends of said chain being driven by said double acting hydraulic cylinder to control the direction of the front wheels,

said hydraulic drive means also including a chain simultaneously engaging the sprockets joined to the yokes carrying the rear wheels and a double acting hydraulic cylinder driving the ends of the last mentioned chain for controlling the direction of the rear wheels,

21 pair of steering wheels hydraulically coupled for separately controlling each of said double acting hydraulic cylinders, said steering wheels being disposed on said frame in facing relation, and

valve means for controlling the operation of said hydraulic drive means, said valve means being located between said steering wheels for simultaneous operation thereof and the said steering wheels by one operator.

17. The vehicle according to claim 16 further including tie down means for securing said frame in a fixed position relative to the working surface including means operated by said tie down means for disabling said hydraulic drive means and said hydraulic steering means when said frame is secured to a working surface.

18. The vehicle according to claim 17 further inclurt ing a platform movable in a vertical direction with respect to said frame with motive means for adjustably elevating and lowering said platform, said tie down means further including means operated by said tie down means for disabling said motive means except when said tie down means secures said frame to said working surface.

19. A positionable vehicle comprising:

a frame,

front support means carrying a pair of front wheels upon which said vehicle is movable,

rear support means carrying a pair of rear wheels upon which said vehicle is also movable,

hydraulic steering means for independently controlling the direction of orientation of said pair of front wheels and of said pair of rear wheels,

hydraulic drive means for rotating at least a selected pair of wheels for moving said vehicle,

1 1 1 2 a common hydraulic supply for said hydraulic steering References Cited means and said hydraulic drive means, and UNITED STATES PATENTS tie down means for securing said frame in a fixed posi- 3 095 945 7/1963 Mitchell tion relative to a Working surface upon which said 3:159:110 12/1964 Wylie v i le i m v l 5 3,237,718 3/1966 Pearson 182-36 20. The vehicle according to claim 19 further includ- 3,245,355 4/1966 Cousins et a1. 182--36 ing a platform supported at one side of said vehicle and wherein said vehicle is counterweighted for supporting REINALDO MACHADO Prmary Exammersaid platform, said tie down means being located on the 10 U.S. Cl. X.R. opposite side of said vehicle from said platform. 18 -17, 145 

